One of the features touted by Magento is the api exposed via both XML-RPC and SOAP. I quickly (and successfully) tested the SOAP interface using the amazingly complete (and free) soapUI. I wanted to use XML-RPC, and decided to build a test client in Java. While trying to build a client, using the apache ws-xmlrpc library, I ran into a roadblock. The initial login and some other calls would work just fine, but some calls such as product.info would always cause an exception, similar to: